U.S. patent application number 13/000251 was filed with the patent office on 2011-06-02 for multiple-screw extruder.
Invention is credited to Werner Bamberger, Michael Baumeister, Ludwig Eckart, Gunter Oedl.
Application Number | 20110128812 13/000251 |
Document ID | / |
Family ID | 41205536 |
Filed Date | 2011-06-02 |
United States Patent
Application |
20110128812 |
Kind Code |
A1 |
Eckart; Ludwig ; et
al. |
June 2, 2011 |
MULTIPLE-SCREW EXTRUDER
Abstract
An improved multiple-screw extruder, in particular a twin-screw
extruder comprises a housing. Several housing bores are located in
at least one section within the housing. The housing bores overlap
at least along a partial axial length of the housing. One extruder
screw is arranged in each of the several housing bores. At least
two motors are provided for the at least two extruder screws. A
synchronizing and torsion transmitting device, by means of which
both cooperating extruder screws can be synchronized, is provided
on both the inlet side and the discharge side.
Inventors: |
Eckart; Ludwig; (Traunstein,
DE) ; Bamberger; Werner; (Traunstein, DE) ;
Baumeister; Michael; (Traunstein, DE) ; Oedl;
Gunter; (Salzburg, AT) |
Family ID: |
41205536 |
Appl. No.: |
13/000251 |
Filed: |
May 27, 2009 |
PCT Filed: |
May 27, 2009 |
PCT NO: |
PCT/EP09/03779 |
371 Date: |
February 2, 2011 |
Current U.S.
Class: |
366/84 ;
366/83 |
Current CPC
Class: |
B29C 48/404 20190201;
B29C 48/435 20190201; B29C 48/41 20190201; B29C 48/08 20190201;
B29C 48/2522 20190201; B29C 48/395 20190201; B29C 48/252 20190201;
B30B 11/241 20130101; B29C 48/2526 20190201; B29C 48/09 20190201;
B29C 48/425 20190201 |
Class at
Publication: |
366/84 ;
366/83 |
International
Class: |
B29B 7/80 20060101
B29B007/80 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2008 |
DE |
10-2008-029-130.7 |
Claims
1. Multiple-screw extruder comprising: a housing, a plurality of
housing holes provided at least in a portion of the housing, the
housing holes overlapping at least in a partial axial length of the
housing, an extruder screw arranged in the plurality of housing
holes, at least two motors provided for the at least two extruder
screws, and both at the inlet side and at the discharge side, a
respective synchronization and torsion transmission device that
achieves synchronization of the two co-operating extruder
screws.
2. Multiple-screw extruder according to claim 1, wherein one motor
at the inlet or discharge side drives one of the at least two
extruder screws, and in that the at least one additional motor
drives the at least one other extruder screw at the opposite
discharge or inlet side.
3. Multiple-screw extruder according to claim 1, wherein the at
least one motor drives the at least one extruder screw at the inlet
side and the at least one additional motor drives the same extruder
screw at the discharge side, and in that the at least one second
extruder screw at the inlet and discharge side is connected by the
respective synchronization and/or torsion transmission device
provided at that location.
4. Multiple-screw extruder according to claim 1, wherein the at
least two motors for the at least two extruder screws are both
arranged at the inlet side or are both arranged at the discharge
side, the at least one motor being drivingly connected to the at
least one first extruder screw and the at least one second motor
being drivingly connected to the at least one second extruder
screw.
5. Multiple-screw extruder according to claim 1, wherein the
separate motor associated with the respective extruder screw is
connected to the associated extruder screw rigidly and/or without
any gearing, in the form of a direct drive, wherein the motor shaft
associated with the respective motor is connected in axial
extension to the drive shaft of an associated extruder screw or
merges into it.
6. Multiple-screw extruder according to claim 1, wherein the
extruder screws have at the drive side thereof a drive shaft or a
drive shaft whose bearing shells are sealed with respect to the
housing interior by seals.
7. Multiple-screw extruder according to claim 1, wherein the
extruder screws have at the non-driving side thereof a drive stub
shaft whose bearing shells are sealed with respect to the housing
interior by seals.
8. Multiple-screw extruder according to claim 6, wherein the seals
are configured at the discharge side to take up the increased
pressures and/or thermal loads which occur at that location.
9. Multiple-screw extruder according to claim 8, wherein the seals
are constructed at the discharge side as cascade seals and/or as
cooling gap seals.
10. Multiple-screw extruder according to claim 1, wherein the seals
on the drive shaft or the drive shaft and on the non-driven stub
shaft are arranged adjacent to the housing interior.
11. Multiple-screw extruder according to claim 1, wherein the
synchronization and torsion transmission device is arranged in the
region of the drive shaft and/or the drive, to drivingly connect
the extruder screw to the associated motor.
12. Multiple-screw extruder according to claim 1, wherein the
synchronization and torsion transmission device is provided in the
region of the stub axle which protrudes axially at an end face at
the non-driven side of an associated extruder screw in an axial
direction relative to the bearing of the extruder screw.
13. Multiple-screw extruder according to claim 11, wherein the
synchronization and torsion transmission device is arranged in a
housing extension which is fitted to the end faces of the extruder
housing.
14. Multiple-screw extruder according to claim 13, wherein the
outermost bearing for the drive shaft or the drive shaft and the
stub axle is provided in the region of the housing extension, and
in that another bearing which is located nearer the extruder
interior at the opposite side of the synchronization and torsion
transmission device is accommodated in the end-face passage region
of the extruder housing.
15. Multiple-screw extruder according to claim 1, wherein the
connection of two extruder screws is carried out by the
synchronization and/or torsion transmission device in the form of a
rotating belt, chain or the like.
16. Multiple-screw extruder according to claim 1, wherein the
multiple-screw extruder comprises at least two contra-rotating
extruder screws which are driven in opposite directions of rotation
by the motors.
17. Multiple-screw extruder according to claim 1, wherein the
synchronization and/or torsion transmission devices comprise
gear-wheels, a gear-wheel which meshes with the gear-wheel which is
arranged at the same height in a rotationally secure manner on the
adjacent extruder screw being arranged in a rotationally secure
manner at the inlet side and at the discharge side respectively
both on the motor-side drive shaft and on the stub shaft which is
located opposite relative to the drive side.
18. Multiple-screw extruder according to claim 1, wherein the
multiple-screw extruder comprises at least two synchronous extruder
screws which are driven in the same direction of rotation by the
motors.
19. Multiple-screw extruder according to claim 1, wherein the
synchronization and/or torsion transmission devices comprise
gear-wheels, a gear-wheel being arranged in a rotationally secure
manner at the inlet side and/or at the discharge side respectively
on the drive shaft and/or the stub shaft, which gear-wheel is in
engagement with the gear-wheel which is arranged at the same height
in a rotationally secure manner on the adjacent extruder screw,
with a redirecting pinion gear being interposed or with two
opposing redirecting pinion gears which each mesh with both
gear-wheels being interposed or by an internally-toothed
gear-wheel.
20. Multiple-screw extruder according to claim 1, wherein the two
drive devices are arranged in an axially displaced manner in order
to drive co-operating adjacent screws in an axial direction of the
associated drive axles, preferably in such a manner that the two
drive devices do not overlap each other when viewed perpendicularly
relative to the associated drive shaft.
21. Multiple-screw extruder according to claim 1, wherein there are
provided at least one drive device and an associated extruder screw
which are drivingly connected to each other by means of a cardan
shaft.
Description
[0001] The invention relates to a multiple-screw extruder, in
particular a double-screw extruder, according to the preamble of
claim 1.
[0002] Extruders in general and double-screw extruders in
particular are well known. They are used in particular for
plasticizing plastics material which can then be further processed
in a subsequent step. Such extruder arrangements are also used, for
example, for producing plastics films, the plasticized plastics
material which is discharged from the extruder being able to be
processed by means of a cooling roller and a subsequent stretching
arrangement to form a plastics film.
[0003] In multiple-screw extruders generally and double-screw
extruders in particular, the individual extruder screws are
generally driven by means of a motor gearing unit. This is
necessary in order to drive the extruder screws synchronously
within narrow tolerances.
[0004] There is generally provided for that purpose a
correspondingly large motor, downstream of which there is connected
a gearing arrangement as mentioned, by means of which it is
possible to distribute force between the individual extruder screws
and it is possible to confer on the extruder screws the desired
direction of rotation.
[0005] Such gearing arrangements can be constructed, for example,
in such a manner that a drive shaft of a motor arrangement
distributes the torque directly to a first output shaft which is
associated with an extruder screw and, via an intermediate wheel,
to a second output shaft which rotates in the same direction, by
means of which a second extruder screw is caused to rotate. In that
case, for example, a so-called synchronous double-screw extruder
would be involved.
[0006] Another preferred embodiment is a so-called contra-rotating
double-screw extruder, wherein the screws rotate in opposite
directions by means of the gearing and the geometry of the screws
is adapted accordingly.
[0007] In principle, EP 0775569 A1 disclosed a double-screw
extruder which constitutes a device of the type mentioned in the
pre-characterizing clause of claim 1. That example sets out two
extruder screws which taper in a conical manner and which are
arranged at a slight angle, that is to say, not parallel relative
to each other, and whose rotating screws overlap in a central
portion and co-operate with each other. A drive motor which causes
the relevant screw to rotate is associated with each extruder screw
at the same side. A gear-wheel is provided between the two extruder
shafts and the motors, respectively, so as to be supported on a
drive shaft, the two gear-wheels associated with the two extruder
shafts engaging with each other. Therefore, a synchronization
device is provided for the two rotors by those two gear-wheels in
order to ensure that the two extruder screws co-operate with
correct rotation and the two screws which engage with each other
cannot collide with each other.
[0008] Unlike that prior art, the two extruder shafts may also be
arranged parallel with each other, the diameter of the rotating
helical screws not tapering from the driving side in that case.
[0009] Accordingly, an object of the present invention is to
provide a multiple-screw extruder in general and a double-screw
extruder in particular, wherein it is possible to drive a plurality
of extruder screws, that is to say, at least two extruder screws,
with relatively little complexity. The synchronous speed of the
screws is also intended to be able to be kept within very narrow
tolerances at different operating moments.
[0010] The object is achieved according to the invention in
accordance with the features set out in claim 1. Advantageous
constructions of the invention are set out in the dependent
claims.
[0011] According to the invention, a synchronization and torsion
transmission device is provided between the two screw axes, firstly
at the inlet side and secondly at the discharge side. That
synchronization and torsion transmission device preferably
comprises two mutually engaging gear-wheels in the case of a
non-synchronous double-screw extruder and preferably comprises
three mutually engaging gear-wheels in the case of a synchronous
double-screw extruder, one gear-wheel being connected in a
rotationally secure manner to one extruder shaft and one gear-wheel
being connected in a rotationally secure manner to the other
extruder shaft.
[0012] Therefore, a force transmission which also serves to bring
about the desired synchronization is also always carried out via
those gear-wheels.
[0013] It is further provided that a corresponding number of motors
is provided for the corresponding number of extruder screws, at
least one motor being associated with each extruder screw.
[0014] There is preferably provision, in a double-screw extruder,
for one motor to be connected with direct driving to the first
extruder screw, for example, at the inlet side of the screw
extruder, and for a second motor to be connected to the second
extruder screw at the discharge side via a direct drive.
[0015] The direct drives mentioned and the synchronization and
torsion transmission device are supported by bearings, the bearings
preferably being able to be integrated in the direct drives.
[0016] Finally, there are also provided seals for sealing the
bearing shells with respect to the melt, the seals having to be
configured accordingly for relatively high pressures at the
discharge side, and consequently high-pressure side, that is to
say, preferably extending over a longer axial sealing path relative
to the extruder shaft than at the inlet side.
[0017] In particular, the seals may also be in the form of cascade
seals in order to be able to take up the pressures, particularly at
the outlet or discharge side, which may be, for example, in the
order of magnitude of up to 60 bar during normal operation and up
to 150 bar during heavy-load operation, it being possible for
thermal loads of up to 300.degree. C. and more to occur.
[0018] In principle, it would also be possible to arrange the two
motors at the same side, for example, the inlet or discharge side
of the screw extruder, in that case the two synchronization and
torsion transmission devices which are associated near the inlet
side and near the discharge side preferably being provided in the
form of gear-wheels.
[0019] Finally, it would also be possible, for example, in a
double-screw extruder, to arrange one motor at the inlet side and
the other motor at the discharge side of the same extruder shaft,
preferably to connect it thereto with direct driving, a second
extruder screw being connected and driven via the two
synchronization and torsion transmission devices mentioned in the
form of two pairs of gear-wheels which are associated with the
inlet side and discharge side, respectively.
[0020] The invention is described in greater detail below with
reference to embodiments. The drawings show the following in
detail:
[0021] FIG. 1: is a top view of a first schematic embodiment of a
multiple-screw extruder according to the invention in the form of a
double-screw extruder having two extruder screws which are arranged
parallel with each other;
[0022] FIG. 1a: is a partially cross-sectioned illustration of the
two mutually engaging gear-wheels which are arranged on
corresponding shafts of the extruder screws driven with each other
both at the inlet side and at the discharge side;
[0023] FIG. 2: is a view rotated through 90.degree. in accordance
with the arrow II in FIG. 1 with an inlet and discharge opening
provided as an alternative;
[0024] FIG. 3: shows an embodiment which is modified with respect
to FIG. 1 and in which the two motors are arranged at the same side
of the screw extruder;
[0025] FIG. 4 shows a further modified embodiment, in which the two
motors are provided at the two opposite end faces of an individual
extruder screw and the second extruder screw is connected at the
inlet side and discharge side via a synchronization and/or torsion
transmission device;
[0026] FIG. 5: shows a modified embodiment, in which there are
driven together not two contra-rotating extruders but instead two
synchronous extruders using at least one or, for example, two
additionally provided redirecting pinion gears;
[0027] FIG. 6: is a cross-section view for clarifying the drive
connection between the two extruder screws using a redirecting
pinion gear;
[0028] FIG. 7: is an illustration corresponding to FIG. 6 using two
redirecting pinion gears; and
[0029] FIG. 8: is another illustration relating to a synchronous
extruder using an internally-toothed gear-wheel.
[0030] FIGS. 1 and 2 show a first schematic embodiment.
[0031] In the construction variant according to FIG. 1, there is
shown a multiple-screw extruder 1 which is constructed in the
manner of a double-screw extruder 1' in the embodiment
illustrated.
[0032] The multiple-screw extruder 1 comprises a housing 3, in the
longitudinal direction of which there are arranged two screws 5,
that is to say, a first extruder screw 5a and a second extruder
screw 5b, which have screw axes 5' which extend parallel with each
other in the embodiment illustrated.
[0033] The screws 5 are in engagement with each other, that is to
say, in a so-called engagement portion 7, in which there are
constructed the screw threads which are generally formed on the
screws, extend helically and are not shown in greater detail in the
drawings.
[0034] In other words, the screws 5 comprise in known manner a
so-called screw core, on which a screw thread which protrudes above
the screw core in a radial direction is formed so as to extend in a
peripheral direction. Consequently, one screw thread engages in the
intermediate space between two helix portions of a screw thread of
an adjacent screw, that is to say, without any contact.
[0035] In the embodiment illustrated, therefore, the screw bodies
(which are also sometimes referred to as the screw core) are
constructed so as to be cylindrical. In a different manner, the
screws or at least the screw bodies could also be constructed so as
to be slightly conical so that the screw axes 5' are not orientated
parallel with each other but are instead orientated at an acute
angle relative to each other generally of only a few degrees. The
screws, that is to say, the screw bodies or the so-called screw
cores, are then formed in a slightly conical manner so that the
associated central or rotation axes 5' in the embodiment which is
not shown in greater detail in the Figures then define an acute
angle of, for example, less than 20.degree. (in particular less
than 15.degree. or less than) 10.degree.). In the embodiment in
FIG. 1, however, the central axes 5' are parallel with each
other.
[0036] The granulate to be processed can be supplied to the housing
interior 3', for example, via a supply channel 11, which granulate
is then provided by the screws and is conveyed by the
contra-rotating rotation movement of the co-operating screws 5
along the screws 5 to the outlet side, that is to say, to an outlet
channel 111 at the discharge side where the melt is discharged.
[0037] In other words, therefore, FIG. 1 shows a double-screw
extruder which comprises a housing 3 having a housing interior 3'
in the form of two housing holes which are provided at least in a
portion of the housing 3. Those housing holes overlap at least in a
partial axial length of the housing 3, forming the engagement
portion 7 mentioned, one of the extruder screws 5 mentioned, that
is to say, the extruder screw 5a or 5b in the embodiment
illustrated, being arranged in each of the two housing holes,
respectively.
[0038] In the embodiment illustrated according to FIGS. 1 and 2,
the first extruder screw 5a is driven at the inlet side 25a with a
motor M1 associated therewith, whereas the second extruder screw 5b
is driven by means of a motor M2 at the discharge side 25b of the
double-screw extruder. Those motors M1 and M2 comprise in the
embodiment illustrated electric motors which can be controlled, for
example, by means of an electronic control device (not shown in
greater detail).
[0039] In the embodiment shown according to FIG. 1, the two screws
5a, 5b each have a drive shaft 9 which is arranged in corresponding
housing holes and sealed at those locations, That drive shaft 9
simultaneously constitutes the drive shaft 19 which may comprise
the motor output shaft. In other words, the motors M1 and M2 are
directly connected to the screw 5a or 5b which is driven thereby
rigidly via the drive shaft 19 or the drive shaft 9 or the shafts
19 already constitute the rotor of a direct drive constructed in
this manner. In those embodiments according to FIGS. 1 and 2 and
the subsequent embodiments according to FIGS. 3 and 4, therefore,
the two motors M1 and M2 drive the two extruder screws 5a and 5b in
opposite directions of rotation. In this regard, they are so-called
"contra-rotating extruders".
[0040] However, it can also be seen from the drawing that the
extruder screw 5a, 5b at the motor side is driven not only via a
drive shaft 9 or a drive shaft 19 (coming from the motor), but
instead that, at the opposite end face, the extruder screw 5a, 5b
merges at the non-driven side thereof into an extended bearing
shaft or stub bearing 119 which also serves to support the extruder
screw, on the one hand, and to bring about the synchronization
and/or torsion transmission, on the other hand, which will be
further discussed below.
[0041] It can be seen in the drawings that corresponding seals have
to be provided in order to seal the bearing shells with respect to
the melt, that is to say, with respect to the extruder housing
interior 3'. For instance, the drive axle 9 or the drive shaft 19
is sealed at the inlet side 25a by means of an inlet-side seal 29,
that seal 29 preferably being positioned on the drive shaft 9, that
is to say, on the drive shaft 19, directly beside the housing
interior 3'. The non-driven stub shaft 119 of the adjacent second
extruder screw 5b, which shaft 119 is used for bearing, is also
sealed at the inlet side 25a by means of such an inlet-side seal 29
with respect to the housing interior, that is to say, the melt,
also preferably being positioned on the stub axle 119 directly
beside the housing interior 3.
[0042] There are also provided, at the discharge or high-pressure
side, corresponding shaft seals 39 which are accordingly configured
so as to withstand high pressure and which also have to withstand
the thermal loads occurring of, for example, up to 300.degree. C.
The pressures may reach 60 bar during normal operation and 150 bar,
for example, during high-load operation. Therefore, the seals 39
which are provided at the discharge side 25b for the non-driven
stub axle 119 of the first extruder screw 5a and for the drive
shaft 9 or the drive shaft 19 of the second motor M2 are
illustrated over a relatively large axial length. In this instance,
for example, cascade seals can also be used, which is known in
principle.
[0043] Those seals are also preferably arranged so as to be
positioned on the shafts 9, 19 or 119 directly beside the housing
interior 3'.
[0044] There will be further discussed below bearings for the
shafts, a synchronization and a torsion transmission device.
[0045] As can be seen from FIGS. 1, 1 a and 2, for example, the
drive shaft 9 or drive shaft 19 which is associated with the first
motor M1 at the inlet side 25a and which has a first torsion
support 35 is preferably provided in the form of a gear-wheel 39.1
which is arranged in a rotationally secure manner on the drive
shaft 9 or the drive shaft 19 and which co-operates, particularly
meshes, with a transmission-side torsion support 36 preferably also
in the form of another gear-wheel 39.2 which is arranged in a
rotationally secure manner on the stub shaft 119 of the second
extruder screw (opposite the motor M2) and thereby also brings
about a desired synchronization between the two extruder screws so
that both extruder screws 5a and 5b are driven at the same speed,
that is to say, the same rotational speed, but in opposite
directions of rotation.
[0046] An identical device is also provided at the discharge side
25b. A drive-side torsion support 35 for the drive shaft 9 driven
by the motor M2 or the driven drive axle 19 is also provided at
that location for the driven second extruder screw 5b, again
preferably also in the form of a gear-wheel which rotates in a
rotationally secure manner and which co-operates, in particular
meshes, with a transmission-side torsion support 36 at the
non-driven end in the form of the stub shaft 119 of the first
extruder screw 5a in order also to implement in this instance a
force transmission device in the form of a synchronization device
and a torsion transmission device between the two extruder screws.
The two gear-wheels 39.1 and 39.2 which engage with each other and
which are illustrated in FIG. 1a are again also used in this
instance for the synchronization and torsion transmission device
35, 36.
[0047] Beside those transmission-side and drive-side torsion
supports 35, 36, which are also sometimes referred to below as
synchronization and torsion transmission devices, there are
provided at both sides inner screw bearings 45 (which are located
nearer the housing interior 3') and outer screw bearings 46 (that
is to say, which are located remote from the housing interior 3')
on the drive shafts 9, that is to say, both on the drive shafts 19
and also on the non-driven stub shafts 119.
[0048] FIG. 1 shows that, for example, the inlet channel 11 for
supplying the granulate to be provided at the inlet side is
provided in such a manner that it provides a connection with
respect to the housing interior 3' in a radial direction relative
to the extruder screws (or at least with a predominantly radial
component), that is to say, located at least substantially in a
plane in which the central axes 5' of the two extruder screws 5a,
5b are also located. Accordingly, the discharge channel 11 at the
discharge side is again preferably also provided in a radial
direction relative to the extruder screws (or with a relatively
large component at least in the radial direction), that discharge
channel 111 being located in the embodiment illustrated at the
opposite longitudinal side of the screw extruder, that is to say,
opposite the inlet channel 11.
[0049] An alternative inlet and discharge channel 11', 111' which
is reproduced in FIG. 2 as an alternative construction is
illustrated with broken lines in FIG. 1.
[0050] This shows that the inlet channel 11' and the discharge
channel 111' extend in a vertical direction or at least
predominantly in a vertical direction, that is to say, the inlet
channel preferably leads in a downward direction to the housing
interior which is located below and, at the discharge side, the
discharge channel 111 also at least predominantly extending in a
vertical direction or preferably extending exactly in a vertical
direction discharges the extruder material provided outwards.
[0051] With reference to the embodiment according to FIG. 3, it is
shown that, unlike FIG. 1, both drive motors M1 and M2 can be
arranged at the same side of the screw extruder, for example, at
the discharge side 25b in accordance with the embodiment according
to FIG. 2. In the same manner, the two motors M1 and M2 can also
both be provided at the inlet side 25a so as to be associated with
the two extruder screws 5a, 5b. The other structure otherwise
corresponds to the embodiment according to FIGS. 1 and 2. Should
the motor housings have a larger diameter than the spacing of the
two extruder axes, there could also be selected an arrangement in
which one drive shaft 9, that is to say, one drive shaft 119, is
extended in an axial direction so that one motor further becomes
arranged so as to be offset in a corresponding axial length of the
other motor with respect to the other motor, that is to say, at the
height of the motor which is located nearer the extruder housing
consequently only the drive shaft 9 or the drive shaft 119 extends
past that motor.
[0052] With reference to the embodiment according to FIG. 4, it is
further schematically shown that both motors M1 and M2 at the inlet
and the discharge side can be associated with a single extruder
shaft, for example, the extruder shaft 5a, the second screw
extruder 5b being connected via the synchronization and/or torsion
transmission device 35, 36 which is provided at the inlet and
discharge side and thereby also being driven in a synchronous
manner.
[0053] In both cases, additional gear-wheels 39.1 and 39.2 are
shown therefor, with one gear-wheel 39.1 being arranged in a
rotationally secure manner, for example, for the drive shaft 9, 19,
that is to say, is connected in a rotationally secure manner to one
screw 5a and the second gear-wheel 39.2 which engages therewith is
connected to the second screw 5b in a rotationally secure manner,
for example, in that it is positioned in the region of the stub
axle 119.
[0054] Owing to the above-mentioned gear-wheels 39.1 and 39.2 which
engage with each other, there will be ensured a forced relative
orientation including torsion compensation of the screws so that
the screw threads cannot collide with each other.
[0055] It can also be seen from the embodiments that the housing 3
comprises a central housing portion having an end-face end region,
in which the drive shaft 9 or the drive axle 19 and the non-driven
stub axle 119 are supported by the bearings 45 described and are
sealed with respect to the extruder interior. A cover or housing
extension 103, in which the synchronization and torsion
transmission device 35, 36 and, via the outer bearings 46, the end
of the non-driven stub axle 119 or the nearest bearings 46 at the
motor side for bearing the shafts in a corresponding receiving
space are accommodated, subsequently adjoins the inlet and
discharge side by means of the seals 29, 39 in axial extension. The
bearing 45 which is located at the inner side relative to the
synchronization and torsion transmission device 35, 36, that is to
say, which is located nearer the interior 3' of the extruder
arrangement, is preferably arranged directly adjacent to the end
face 33 of the housing portion 3 (with the cover-like housing
extension 103 removed).
[0056] Reference is made below to FIG. 5 which shows an embodiment
of a double-screw extruder that is comparable in terms of the basic
construction, with the double-screw extruder shown in FIG. 5 not
having, unlike in FIG. 1, a so-called contra-rotating extruder (in
which the two extruder screws are driven in opposite directions of
rotation) but instead has a synchronous extruder, in which the two
extruder screws 5a and 5b are driven not only at the same speed but
above all in the same direction of rotation with respect to each
other.
[0057] This can be carried out according to FIG. 5 by a third
gear-wheel 39.3, the synchronization and torsion transmission
devices 35, 36 in the form of the preferably used gear-wheels 39.1
and 39.2 not meshing with each other, unlike in the embodiment
according to FIGS. 1 and 2, but instead being arranged at least
with small spacing from each other so that a driving connection is
brought about from one gear-wheel 39.1, via the intermediate
gear-wheel or redirecting pinion gear 39.3, to the next gear-wheel
39.3 which is connected to the second extruder shaft in a
rotationally secure manner. This function is shown as a
cross-section in accordance with FIG. 6 for the synchronization and
torsion transmission device 35, 36 both at the inlet and at the
discharge side.
[0058] A particularly symmetrical synchronization and torsion
transmission is brought about if, for example, in the embodiment
according to FIG. 5, unlike the example according to FIG. 6, there
is further used a second redirecting or intermediate gear-wheel
39.3', that is to say, an additional redirecting pinion gear 39.3',
so that there is provided, opposite the first pinion gear 39.3 at
the other side of the two gear-wheels 39.1 and 39.2, an additional
pinion gear 39.3' which also meshes with the two gear-wheels 39.1
and 39.2. The two gear-wheels 39.1 and 39,2 are located themselves
out of engagement with one another.
[0059] In place of that embodiment, it is also possible to
implement a symmetrical force transmission and therefore optimum
synchronization and torsion transmission in that, for example,
unlike FIG. 7, there is used an internally-toothed gear-wheel
39.3'' which meshes with the externally-toothed gear-wheels 39.1
and 39.2, preferably at the opposite regions thereof (that is to
say, regions located further away from each other). In that case,
there would preferably be provided two such internally-toothed
gear-wheels, both at the inlet side and at the discharge side.
However, even mixed systems would be possible so that, for example,
there are used an internally-toothed gear-wheel at the inlet side
or at the discharge side and, at the opposite side, respectively,
that is to say, for example, at the discharge side or the inlet
side according to FIG. 6 or 7, only one redirecting pinion gear or,
for example, two redirecting pinion gears which mesh with the two
synchronous driven gear-wheels 39.1 and 39.2 (that is to say,
moving in the same direction of rotation).
[0060] The operations described with reference to FIGS. 6 and 7 for
a synchronous extruder can also be used in the embodiments
according to FIGS. 3 and 4.
[0061] As is evident from the described embodiments of the
invention, the motors are rigidly connected to the extruder screw
5a or 5b, respectively. If the motors are arranged beside each
other as in the embodiment according to FIG. 3, the diameter of the
individual motors may correspond to the axial spacing of the screws
at the maximum when the housing structure is symmetrical.
Otherwise, the motors would have to be arranged with different
axial spacing with lateral displacement relative to each other so
that a motor housing can in principle also have a diameter which is
greater than the axial spacing of two adjacent screws if the drive
shaft which extends past the motor housing and which leads to a
second motor which is provided with axial displacement has a
smaller outer diameter in that lateral region.
[0062] For example, in the case of a double-screw extruder, it
would also be possible to drive the two motors which are each
associated with a separate extruder screw by means of a cardan
shaft. The diameter of the individual motors can thereby often be
greater than the axial spacing of the screws. In a simplified
embodiment, it would also be possible to connect only one motor to
an extruder screw via a cardan shaft, whereas the second motor is
directly connected to the extruder screw.
[0063] The invention has been described with reference to a double
extruder. However, it may also be a multiple extruder which
comprises more than two extruder screws. In that case, the
implementation variants described may be extended as desired.
Consequently, it is also possible to have a multiple-screw extruder
which comprises at least two extruder screws in addition to at
least one additional extruder screw, in a construction as has been
explained with reference to FIGS. 1 to 4.
[0064] The various embodiments have been explained for the
situation that there are used for the synchronization and torsion
transmission device 35, 36 either the gear-wheels 39.1 and 39.2
which mesh directly with each other (in extruder screws driven
contra-rotatingly) or the gear-wheels 39.1, 39.2 and 39.3 or 39.3'
or 39.3'' (in extruder screws which are driven synchronously).
Irrespective of that, however, it is also possible to use all other
technical means to bring about a corresponding synchronization and
torsion transmission device 35, 36, for example, in the form of
chains, belts or other suitable synchronization and drive
connections.
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